1. Field of the Invention
The invention is directed to a tilting segment for a shaft bearing device and a shaft bearing device.
2. Description of the Prior Art
A shaft bearing device for slide bearing support of a rotating shaft comprising a bearing base body and a plurality of tilting segments received at the bearing base body and positioned one behind the other in circumferential direction is known from U.S. Pat. No. 6,361,215 B1. Each of the tilting segments has a slide bearing face bounded on one side by a segment leading edge extending in axial direction and a segment trailing edge extending likewise in axial direction and on the other side by lateral edges extending in circumferential direction between the segment leading edge and the segment trailing edge. It is further known from U.S. Pat. No. 6,361,215 B1 that a so-called directed lubrication or a so-called grooved lubrication can be used at a shaft bearing device of this type. The grooved lubrication has the advantage of a better damping of vibrations, while directed lubrication has the advantage of lower oil consumption and, therefore, lower power loss. In order to provide a shaft bearing device with lower power loss and reduced vibration behavior at the same time, a groove extending in axial direction, or leading edge groove as it is called, via which the tilting segment is supplied with oil is provided according to U.S. Pat. No. 6,361,215 B1 at the start of the slider surface of the tilting segment adjacent to the segment leading edge. Likewise introduced into the slide bearing face are grooves which extend in circumferential direction, run adjacent to the lateral edges and extend up to the region of the trailing edge of the tilting segment.
These grooves, which extend in circumferential direction in the tilting segments and which are known from U.S. Pat. No. 6,361,215 B1, reduce the lateral outflow of oil from the respective tilting segment. With this reduced lateral oil flow, a defined amount of oil is conveyed into the divergent lubricating gap at the end of the segment, where it provides for improved vibration damping of possible vibrations known as synchronous vibrations and subsynchronous vibrations.
A further shaft bearing device with tilting segments is known from U.S. Pat. No. 6,485,182 B1. According to this prior art, the tilting segments are supplied with oil via a gap formed between adjacent tilting segments.
The shaft bearing devices with tilting segments known from the prior art have the problem that the tilting segments, which are loaded relatively lightly in operation, have a tendency toward segment flutter, as it is called.
Segment flutter describes subsynchronous vibrations induced in the bearing itself. These subsynchronous vibrations occur as a result of the continuous oscillation of the unloaded tilting segments between two different balance points. The tilting segment cannot occupy a stable position and is therefore unstable. Segment flutter can occur, for example, as a result of deficient lubrication. This is the case when the lubricating gap cannot be completely filled with lubricant. This can occur when the eccentricity between the center point of the shaft and the center point of the bearing is very great. In this case, the lubricating gap widths between the unloaded tilting segment and loaded tilting segment can deviate greatly from one another so that the amount of lubricant supplied can no longer completely fill the highly enlarged lubricating gap of the unloaded tilting segment.
In extreme cases, segment flutter leads to solid contact between the segment sliding face and the shaft surface and thus to damage or even destruction of the segment.
One possibility for reducing segment flutter consists in outfitting the bearing with a grooved lubrication so that the entire bearing is filled with lubricant. In this case, with regard to construction, a lateral seal is usually inserted at the axial bearing ends of the bearing housing that restricts the lateral flow of lubricating oil that is heated via the tilting segment out of the bearing housing. Accordingly, the lubricating film temperature is appreciably higher owing to the restricted outflow of warm lubricating oil from the slide bearing and, further, the power loss is also appreciably higher because of the increased fluid friction. Mechanical adjustments of this type for suppressing or reducing segment flutter are very costly.
Heretofore, there were no known solutions by which so-called segment flutter could be securely and reliably prevented by simple means.